What Facebook knows about you and how to find out?

If the advertisements on your Facebook newsfeed appear remarkably relevant, it’s because the social network giant knows you well. Facebook amassed an estimated $26.9 billion in ad revenue in 2016 alone by mining its vast troves of data on its 1.86 billion users to sell targeted information to advertisers they use to offer products and services based on your personal tastes.

What Facebook does with your data remains a subject of debate, but the data that it has is disturbingly detailed.

1.) Who you, your family and your friends are

The basis of your profile is your on-site behaviour, covering the profile information you provide, the advertisements you click on, the events you create and attend, the items you like and the information you post.

This behaviour reveals your age, gender, language and educational level, the electronic device you use and how you connect to the internet

Your posts and profile provide the foundation of your Facebook data footprint, but the company compiles a vast array of information from other sources to add personal details far beyond those you knowingly upload.

Your online behaviour and information from third-party sources are mixed in to tell Facebook your job, whether you’re married, engaged or soon celebrating an event, and whether you're a parent or expecting to be one soon.

It also knows who else is in your family, how far away they live and their coming anniversaries, and who your friends are and which of them is in a new relationship, home, or soon celebrating a birthday.

2.) Your finances and spending habits

It pays data brokers such as Experian and Epsilon for extra information they’ve compiled over years gathering extra information from government records, surveys and commercial sources such as magazine subscription lists. This tells them where you shop, what you buy, and whether you own a car.

It also knows the value, size, composition and type of property you live in, and when that property was built.

It not only knows what you have but also what you want, by understanding your tastes and when you will likely be looking to upgrade something

Your financial information is all up for grabs. Facebook can predict what you invest in, whether you have a credit card and if it's in debit, you income and net worth, if you are a member of a credit union, national bank or regional bank.

3.) The websites you’ve visited and the apps you’ve used

Your online activity tracked by Facebook isn't limited to the social media site alone. If you ever visit a web page that uses Facebook technologies such as Facebook pixel, both publishers and Facebook can track visits from the users.

Advertisers use the information to craft ads for people who have visited the website or used the mobile app. It covers any page with a "like" or "share" button, which tell Facebook where you're browsing, any downloads of their mobile apps and any purchases from the site or products adding to the shopping cart.

The Facebook family of apps and services also includes Instagram and WhatsApp, both of which add to the company's data dossier.

4.) Were you are and where you have been

Facebook uses location data to help advertisers target people in or near a specific place. This information is revealed by the IP address where you connect to the internet, the GPS and location services on your phone, your check-ins and listed location in your Facebook and Instagram profiles.

Controversy emerged in June 2016 when Facebook first admitted and then denied it was using smartphone location information to suggest friends, but ultimately divulged that it had done briefly the previous year.

5.) Your beliefs

The targeted advertising used by the Donald Trump team before the 2016 US presidential election exposed the value of Facebook data in political campaigning.

If you state your political preference, express a political leaning or like a page associated with one, Facebook uses the information to presume your political views. But the company doesn't only need direct evidence. If you like pages viewed as typical of a certain position that could suggest you share those beliefs. Liking Exxon, for example, may indicate you're more likely to be conservative.

Facebook combines these details with demographic information in order to categorise users as liberal, conservative or moderate. The information is then anonymised and sold to campaign managers and advertisers.

6.) Your secret thoughts

The old adage of 'think before you speak' has earned a new lease of life on social media, where the false security shield of screen and keyboard has led to many a regretful tap of the enter key. Data scientist Vicki Boykis recently revealed that Facebook knows what you were thinking even when you choose not to say it. The company can track your typing to read your mind.

Facebook collects the text as you type it by sending code to your browser that analyses your keystrokes and reports the metadata. It includes deleted posts, comments, and check-ins. The company calls these unpublished thoughts "self-censorship", and has previously used the data to study human behaviour.

The total incoming data adds up to around 600 daily terabits if the 2014 estimates of Facebook engineers are accurate. According to Boykis' calculations, this is the equivalent of uploading 193 million copies of the novel War and Peace per day.

What Facebook knows about you: How to find out?

Facebook provides a board outline of the information it collects in its Data Policy, but doesn't reveal full details of how it works.

You can find out what Facebook thinks about you by going to your ad preferences on the social network. It includes your profile information, categories of interests and advertisers you’ve interacted with as a customer, a website user or just by clicking on their ads. You can also hide advertisements about sensitive topics which you’d rather not see. Facebook users can also block certain types of ads by visiting Facebook ads settings.

The only way to escape the clutches of the Facebook data collectors and their partners is by leaving the social network altogether. Even that won't provide you with a truly clean break. Your data leaves an indelible mark, and once you agree to hand it over you're no longer entitled to get it all back. You can, however, download your entire Facebook data history as a ZIP file, using a self-service tool created by the company.